1. Field of the Invention
The present invention relates to a connective jumper for electrically connecting prescribed two positions of a wiring pattern with each other while avoiding shorting to another wiring region and a method of manufacturing the same.
2. Description of the Prior Art
FIG. 8 is a perspective view showing a conventional connective jumper 1. As shown in FIG. 8, this connective jumper 1, being entirely formed by a metal material, comprises a jumper body 2 which is U-shaped in section and jumper connecting portions 3 outwardly extending from both ends of the jumper body 2. Excepting end surfaces 3a and 3b of the jumper connecting portions 3 and an end surface 2a of the jumper body 2, the connective jumper 1 is plated with Sn or the like.
In view of mass-productivity, such connective jumpers 1 are manufactured as follows: First, plating is performed on the surface of a metal plate 4 of 0.1 to 0.2 mm in thickness, as shown in FIG. 9. Then, the metal plate 4 is punched by a press along phantom lines 5 as shown in FIG. 9, while each segment obtained by such punching is simultaneously shaped by the press to obtain the connective jumper 1 as shown in FIG. 8.
FIG. 10 is a plan view showing a hybrid integrated circuit device 6 carrying such a connective jumper 1, and FIG. 11 is a sectional view taken along the line X--X in FIG. 10. The hybrid integrated circuit device 6 comprises an insulating substrate 7 which is formed thereon with a wiring pattern 8 of a thick film conductor, a thick film resistor 9 etc. A flip chip IC element 10 and the connective jumper 1 are mounted on prescribed portions of the wiring pattern 8. The connective jumper 1 is mounted as follows: Soldering paste 11 obtained by kneading solder powder and flux etc. is coated on a portion of the wiring pattern 8 for carrying the connective jumper 1 by printing etc., and thereafter the jumper connecting portions 3 of the connective jumper 1 are temporarily placed on the coated portion. Then the insulating substrate 7 is heated at a temperature exceeding the melting point of the soldering paste 11 to melt the soldering paste 11, and thereafter cooled to a temperature lower than the melting point of the soldering paste 11 to solidify the soldering paste 11, thereby to electrically and mechanically connect the connective jumper 1 to the wiring pattern 8.
In such a conventional connective jumper 1, the end surfaces 3a of the jumper connecting portions 3 are not plated and hence the end surfaces 3a are insufficiently connected with the soldering paste 11 when the connective jumper 1 is soldered onto the wiring pattern 8, as shown in FIG. 11. Consequently, bond strength between the connective jumper 1 and the wiring pattern 8 is reduced. Therefore, when an endurance test is performed upon completion of soldering through temperature cycling of at least 200 cycles with a cycle of temperature change of -40.degree. C. to 125.degree. C., for example, shearing stress is applied to junctions between the jumper connecting portions 3 and the soldering paste 11 due to difference in thermal expansion coefficient between the insulating substrate 7 and the connective jumper 1, to cause cracking in the soldering paste 11 and the wiring pattern 8 along the end surfaces 3a. Thus, the wiring pattern 8 is disconnected or the soldered portions are displaced in the worst case. Further, since the end surfaces 3a linearly extend along the cross direction of the connective jumper 1, cracking caused on the soldering paste 11 along the end surfaces 3a rapidly progresses while it is difficult to visually inspect such cracking.